Biology Reference
In-Depth Information
Early Gonadal
differentiation
Genetic sex
determination
Birth
Critical window of Brain
sexualization
Life
history
Neurogenic activity
Radial glial cells
Aromatase activity
Very labile genetic
sex determination
Late gonadal differentiation with possibility of sex
change
L
arge window of brain sexualization
Life
history
Hatching
Neurogenic activity
Radial glial cells
Aromatase activity
Fig. 1.
Ontogenetic pathways of sex determination and differentiation in mammals and
fi shes. Note the differences in the critical window of brain sexualization (adopted from Le
Page et al., 2010)
Color image of this figure appears in the color plate section at the end of the topic.
the need for genome-wide linkage analysis and search for more than one
sex determining gene located on different chromosomes of fi shes.
In the context of sex determination in fi shes, the hermaphrodites are of
special interest. The hitherto cytogenetic search for the sex chromosomes in
a dozen or so hermaphroditic fi shes has identifi ed the presence of an XX/
XO system in the protogynic sequential labrid
Coris julis
only
(see Devlin
and Nagahama, 2002). It remains to be seen whether
C. julis
is a somatic
XX hermaphrodite producing XX female and XO male progenies due to
non-disjunction of one X chromosome in an embryo and an adult female
resulting in the production of primary and secondary males, respectively
(see Zarkower, 2006).
1.2 Hermaphroditism
In gonochores the male and female reproductive function is discretely
expressed in
different individuals
but
within a single individual
in
hermaphrodites. In fi shes, simultaneous, sequential and serial are the
recognized patterns of hermaphroditism (Fig. 2). The sequentials and
